[S-VC25] International Volcanology

[SVC25-04] Geodetic observations and the inferred geometry of the dyke intrusion associated with the 2020 Taal Volcano eruption

*Lincoln Paul Alcantara Olayta^1,3, Yo Fukushima^1,2 (1.Graduate School of Science, Tohoku University, 2.International Research Institute of Disaster Science (IRIDeS), Tohoku University, Sendai, Japan, 3.Philippine Institute of Volcanology & Seismology (PHIVOLCS), Department of Science & Technology, Philippines)

Keywords:Volcanology, Active Volcano, Geodesy, InSAR

Eruptive ground displacements provide important insight into the geometry and dynamics of the pressure source/s underneath. The deformation associated with the 2020 Taal eruption was well observed using synthetic aperture radar (SAR) data, except for the Taal volcano island (TVI) and the surface fissuring areas SW from TVI where InSAR signals were decorrelated. Utilizing available cGNSS displacements, especially on the island, provides better constraints on the model. ALOS-2 InSAR and cGNSS results observed large displacements on the fissure axis, with maximum horizontal displacements of ~1.52 m and ~0.25 m uplift. A notable subsidence (~0.91 m) on the TVI was also observed by the only surviving cGNSS station during the eruption. Such a deformation pattern is consistent with a deflation of the shallow chamber beneath the island and an intrusion of a dyke on the axis of fissuring. We jointly inverted the cGNSS & ALOS-2 InSAR displacements using the numerical 3D mixed boundary element inversion method via DEFVOLC software, with a two-step modelling scheme to separately model the displacements due to a dyke intrusion and a deflation of the shallow chamber. Our modelling results found a near-vertical NE-SW striking dyke, and a deflating NW-SE striking ellipsoid which had the same geometry from our pre-eruptive model. These results were also consistent with the observed seismicity during the eruption.